A display apparatus such as a liquid crystal display apparatus displays an image typically by controlling a display medium such as a liquid crystal material by using a substrate on which a plurality of electrode lines are provided in a stripe pattern or a matrix pattern. Examples of liquid crystal display apparatuses include those of a passive matrix type and those of an active matrix type.
In a passive matrix liquid crystal display apparatus, each pixel is defined by one of column electrodes arranged in a stripe pattern on one substrate and one of row electrodes arranged in a stripe pattern on the other substrate so as to extend perpendicular to the column electrodes, and the optical transmittance of the liquid crystal layer is modulated for each pixel, thereby displaying an image.
Electrode lines including the column electrodes and the row electrodes are produced through the following steps, for example. A transparent conductive film such as an ITO film is deposited on a substrate by a sputtering method, or the like. A photoresist is applied on the transparent conductive film and is prebaked. The photoresist is exposed to UV light via a mask having a stripe pattern. The photoresist is developed, and unnecessary portions thereof are removed. The exposed transparent conductive film is etched, and the remaining photoresist is peeled off.
Next, an active matrix liquid crystal display apparatus using an active matrix substrate will be described. FIG. 39 is a plan view schematically illustrating a conventional active matrix substrate. The active matrix substrate includes a plurality of pixel electrodes arranged in a matrix pattern, and a plurality of active devices associated respectively with the plurality of pixel electrodes for performing a switching control. In a liquid crystal display apparatus using an active matrix substrate, the optical transmittance of the liquid crystal layer between the pixel electrodes of the active matrix substrate and the opposing counter substrate is modulated for each pixel, thereby displaying an image.
The pixel electrodes are formed by patterning, through a photolithography process, an ITO (indium tin oxide) film or a metal film deposited across the entire surface of the substrate. Therefore, some of the metal material, etc., is wasted. In recent years, there is a strong demand for conserving energy and resources in a display device manufacturing process from an environmental point of view. By eliminating patterning processes as much as possible, it is possible to shorten the process for manufacturing a display device, reduce the number of pieces of manufacturing equipment and reduce the floor area required for installing the manufacturing equipment, thereby reducing the cost for the manufacturing process, and to reduce the amount of contaminant or hazardous substance used or produced in the patterning process, thereby achieving a cleaner process.
On the other hand, there are various image resolutions in terms of definition such as VGA (video graphics array) and XGA (extended video graphics array), and the pixel pitch varies for different resolutions. With the conventional process, it is necessary to provide a suitable photolithography mask and an optimal resist material according to the pixel pitch.
Moreover, some display apparatuses use a pixel division method for realizing a gray scale display. In the pixel division method, each electrode is patterned, or divided into portions, according to the gray scale. For example, when each electrode is patterned into two portions with an area ratio of 1:2, only a gray scale of 1:2:3 is realized, and when it is patterned into three portions with an area ratio of 1:2:4, only a gray scale of 1:2:3:4:5:6:7 can be realized. Thus, the pixel division gray scale display is limited by the initial division of each electrode and the area ratio among the portions thereof.